Tank car heating system



March 31, 1970 H. ROLE TANK CAR HEATING SYSTEM 2 Sheets-Sheet 1 FiledNov. '7, 1967 March 31, 1970 H. RbLE 3,503,381

TANK CAR HEATING SYSTEM Filed Nov. 7, 1967 2 Sheets-Sheet 2 1&4 3/" f /pI 3 Hi5. i7 5 mm J 14hr Fd/a,

United States Patent 3,503,381 TANK CAR HEATING SYSTEM Harry Role,Chicago, Ill., assignor, by mesne assignments, to Union Tank CarCompany, a corporation of Delaware Filed Nov. 7, 1967, Ser. No. 681,450Int. Cl. EOlc 19/45; F24h 1/00 US. Cl. 126--343.5 5 Claims ABSTRACT OFTHE DISCLOSURE This invention relates in general to tank cars. It dealsmore particularly with a system and method for melting partiallysolidified lading in a tank car to facilitate removal of the lading.

Railway tank cars are employed to transport various products havingwidely varying physical and chemical characteristics. Some of theseproducts present few problems in handling, while others are moredifficult. The present invention is concerned with the handling ofproducts which are solid or semi-solid at normal ambient temperaturesand must be melted for introduction to and removal from a tank car.

It is conventional to transport sulfur, for example, by tank car in itsmolten state. More precisely, it is conventional to introduce sulfur toa tank car in its molten state, after which the liquid sulfur solidifiesto a greater or lesser extent against the cooler tank wall while beingtransported, depending upon time en route and ambient air temperature.When the sulfur reaches its destination, a relatively thick, solid crusthas formed on the inner surface of the tank. A molten core remainsinside the crust.

The solidified sulfur must be melted before it can be removed from thetank car. To this end, it is now a well known expedient to employ anoutside heater system on the tank car to melt the solid sulfur. Steam ispassed through a relatively dense conduit system secured to the outersurface of the tank and the heat released from the steam begins to meltthe sulfur crust. A liquid sulfur film forms and gradually increases inthickness on the tanks inner surface. The solid sulfur crust acts as anexcellent insulator, however, and transmission of heat to the liquidcore is greatly impeded. The crust melts slowly.

As the heating process continues, the liquid film becomes thicker andthe ring of solid sulfur loses some of its structural strength. Thesolid ring of sulfur, being supported primarily from its opposite endsat the tank heads, begins to sag at the center of the tank, generatingliquid circulation from the bottom to the top of the tank. Finally, thesolid sulfur ring breaks up and circulation is established between theliquid film and the liquid core. This accelerates the melting process.

The aforedescribed system is eventually effective to completely melt thepartially solidified sulfur. However, it may require up to 48 hours tomelt the crust with normal steam pressure in the heater conduits. Thisconsiderable steaming time increases shipping costs as well as delayingdelivery.

It is an object of the present invention to provide a greatly improvedsystem and method for melting a partially solidified tank car ladingsuch as liquid sulfur or the like. The invention contemplates ahorizontally elongated 3,503,381 Patented Mar. 31, 1970 cylindrical tankhaving substantially less dense external heating complex disposed on itsouter surface. Inside the tank, longitudinally extending fin means areprovided generally co-extensive with a heating conduit or conduitsextending along the base of the tank. The conduit or conduits at thebase of the tank are also preferably inside the tank.

When liquid sulfur is introduced to the tank, the liquid sulfurimmediately begins to solidify at the inner surface of the tank, forminga crust. The crust thickens as additional sulfur solidifies while heat.is dissipated during transport of the lading.

The internal fin means is constructed and arranged so that it extendsupwardly from the base of the tank through this crust. When the tankreaches its destination, heat is applied to the tank through theaforementioned external heating complex by introducing steam to thecomplex, for example. At the same time, steam is passed through theinternal conduit. The crust of solidified sulfur begins to melt at theinner surface of the tank and a film of liquid sulfur forms at thesurface. At the same time, the heat dissipated through the fin or finsis effective to almost immediately melt through the ring of sulfur toits molten core, thus splitting the ring at the tin or fins. Circulationis established between the large liquid core at the center of the tankand the thin liquid film against the tank inner surface. This dynamicaction promotes heat transmission by convection to the exposed innersurfaces of the solidified crust of sulfur lading.

As this process continues, the thickness of the liquid film against thetank inner surface and tin rapidly increases, and the structuralstrength of the solid sulfur, in a split ring configuration, decreasesuntil it can no longer support itself. The solid sulfur begins to act asa beam generally supported at opposite tank heads with large deflectionsat the center of the tank. This movement induces an additional liquidcirculation from the bottom to the top of the tank, which speeds up themelting process and shortly thereafter the split-ring" of sulfur crustdisintegrates. The melting now proceeds more rapidly as the chunks ofsulfur sink to the bottom of the tank where the heat source isconcentrated and the hot liquid sulfur rises to the top of the tank.

In another aspect of the invention, a fin or fins is provided along theroof of the tank, co-extensive with a longitudinally extending conduitwhich may be disposed on the inner surface of the tank or may be mountedon its outer surface. The fin or fins along the roof of the tankfunction in a manner identical to the fin or fins along the base of thetank, almost immediately melting through the crust of solidified sulfurto create another split in the ring. The ring of sulfur is thusvirtually divided into two parts and melting and disintegration of thesolidified crust takes place at an even faster rate.

The invention, together with its construction and method of operation,taken with other objects and advantages thereof, is illustrated more orless diagrammatically in the drawings, in which:

FIGURE 1 is a diagrammatic side elevational view of a heating systemembodying features of the present invention, mounted in place on thetank of a conventional insulated railway tank car, with the tankillustrated in phantom lines;

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE 1;

FIGURE 3 is a sectional view taken along line 3-3 of FIGURE 1;

FIGURE 4 is a view taken along line 4-4 of FIG- URE 1; and

FIGURE 5 is a view similar to FIGURE 3 illustrating a modified form ofthe heating system shown in FIG- URES 1-4.

Referring now to the drawings, and particularly to FIGURE 1, a broadlyconventional structural inner tank for an insulated railway tank car isillustrated generally at 10. The tank comprises a cylindrical bodysection 11 fabricated of steel plate or the like. A concave head section12 is welded over each end of the body section 11. The tank 10 isadapted to receive a liquid lading through the manway 15 on the roof ofthe tank. An unloading fixture 16 on the base of the tank 10 is providedto drain liquid lading from the tank. A siphon and valve nozzlearrangement 17 also on top of the tank 10 can also be used.

Mounted on the tank 10 is a heating system 20 embodying features of thepresent invention. The heating system 20 includes an external conduitcomplex 22 and an internal conduit and fin assembly 24. The tank 10 andsystem 20 are normally encased in insulating material and covered withan outer skin, but for ease of illustration and description of theinvention, the insulating material and skin are not shown. The tank 10is supported from convention-a1 railway trucks (not shown) in a wellknown manner.

The heating system 20 is designed, according to the invention, torapidly melt a liquid lading which has partially solidified in transit.For purposes of illustration the lading described is sulfur which has amelting point of 112.8 degrees centigrade. It should be understood,however, that numerous material which might be transported in tank carsalso solidify at normal ambient temperatures and, accordingly, require aheating system of one type or another to melt any portion which mighthave solidified before the lading has reached its destintion. Suchproducts include parafiins, naphthalene, phthalic anhydride, and manyothers.

In the present example, the sulfur lading is first melted forintroduction to the tank 10 through its inlet facility 15. Immediatelyupon contact with the inner surface 26 of the tank 10, the sulfur beginsforming a crust on the inner surface, since the ambient temperature isnecessarily considerably less than 112.8 degrees C. As the crustthickens, however, it acts as more of an insulator and the rate ofsolidification decreases. As a result, an extensive core of moltensulfur normally remains at the center of the tank when it arrives at itsdestination. When the tank 10 reaches its destination, the solidifiedsulfurcrust must be melted. The heating system 20 embodying features ofthe invention melts this crust at a substantially greater rate thanheretofore possible with heating systems of a broadly similar nature.

The external conduit complex of the system 20 comprises a plurality ofhorizontal steam conduits 30 secured to the outer surface 31 of the tank10. Each of the conduits 30 is a half-oval steel pipe, as best seen inFIG- URES 3 and 4, with its free edges welded to the outer surface 31 ofthe tank.

The horizontal conduits 30 are spaced circumferentially on the surface31 of the tank 10. Four of these conduits 30 are grouped on the base ofthe tank 10 on the opposite side of the center line CL. The remainder ofthe conduits 30 are more widely spaced around the side and top of thetank, with the conduit 30c disposed on the top center line CL. Thesignificance of the positioning of these conduits 30 circumferentiallyof the tank 10 will hereinafter be discussed.

At opposite ends of the tank 10, where corresponding ends of theconduits 30 terminate, circumferentially extending headers 35interconnect the conduits. The headers 35 (and all header sectionshereinafter referred to) comprise channel members into which thecorresponding ends of the conduits 30 extend. The free edges of thechannel member headers 35 are welded to the outer surface 31 of the tank10.

Intermediate the opposite ends of the tank 10 a short circumferentialsection 37 interconnects adjacent inner ends of one-half section of theconduit 30c and a half section of one of the bracketing conduits 30alongside the conduit 30c. Also on the roof of the tank, adjacent itscenter line CL, a conventional valve housing 39 is mounted. The siphonand valve nozzle arrangement 17 is in this housing 39, the inner end ofthe other half section of the conduit 30c and the inner end of a halfsection of the other bracketing conduit 30 are connected by pipes 40into the valve housing 39 where suitable means are provided to passingthe steam through the valve housing 39.

At the base of the tank 10, the inner ends of half sections of thelowermost conduit 30b are joined by short circumferential conduitsections 44 to inlet and drain pipes 46 and 47 on the center line CL ofthe tank 10. Similarly, short circumferential conduit sections 50connect the inner ends of half sections of the lowermost conduit 30a toa pipe assembly 54 and an inlet pipe 55, and an outlet pipe 56. The pipeassembly 54 actually forms a collar around the outlet fitting 16 for thesteaming of the lading in this critical area.

Referring now also to FIGURE 2, inside the tank 10 are provided twoconduit sections 6-4 and 65. Each conduit section 64 and 65 extendsslightly less than one-half the length of the tank 10. The conduitsections 64 and 65 are in alignment with each other longitudinally ofthe tank 10 on the center line CL of the base of the tank. Once again,each conduit 64 and 65 comprises a half oval having its free edgeswelded to the inner surface 26 of the tank.

The outer free ends of each of these internal conduits 64 and 65 haveshort, circumferentially extending conduit sections 69 connectedthereto. The conduit sections 69 are connected in a suitable mannerthrough the tank 10 to the adjacent headers 35 on the outer surface 31of the tank 10.

Adjacent to its inner end, the internal conduit 65 is connected throughthe tank 10 to the external conduit section 44 and, consequently, to theinlet pipe 46. At the same time, the inner end of the internal conduit64 is connected through the tank 10 to the conduit section 50, and,accordingly, to the pipe assembly 54 and the inlet pipe 55.

Mounted on top of each inverted, half-oval conduit 64 and 65, andco-extensive longitudinally with it, is a vertical heat transfer fin 70.As seen in FIGURE 4, each of the fins 70 extends over and is welded tothe upper surface of a corresponding circumferential internal shortconduit section 69.

Each fin 70 is fabricated of a highly conductive alloy and extendsapproximately seven inches up from a corresponding conduit 64, 65 in thepresent illustration. Since the height of the conduits 64 and 65 isapproximately two inches, the overall height of the fin 70 from theinner surface 26 at the bottom center line of the tank 10 isapproximately nine inches. For reasons hereinafter discussed, theoverall height of the fin 70 may vary in various applications of theinvention.

The heating system 20 embodying features of the invention has now beendescribed in detail as to its construction. The operation of the system20 is best understood by considering the hypothetical situation whereinthe tank 10 is being used to transport sulfur.

To transport sulfur in a tank car 10 in a well-known manner, the sulfuris first liquified and introduced to the tank, as has been pointed out.As soon as the liquid sulfur contacts the relatively cooler innersurface 26 of the tank, a crust of solidified sulfur begins to form atthis surface. As the tank 10 proceeds to its destination, additionalliquid sulfur continues to solidify and the crust thickens. Since thecrust itself acts as an insulator, the rate of solidification of thesulfur decreases rapidly with time, however, and a substantiallyextensive core of molten sulfur remains for a considerable period oftime.

It has been found from experience that the crust of solidified sulfurnormally does not become more than six or seven inches thick in averageto average-cold climates;

taking normal maximum trip times into consideration. Accordingly, thefin 70 virtually always extends upwardly into the molten core of sulfurwhen the tank has reached its destination. Where extreme cold isnormally encountered, the height of the fins 70 can be appropriatelyextended to accommodate thicker crusts. When the fins 70 are extendedupwardly, however, heat transfer is limited substantially. Accordingly,it is within the purview of the invention to actually segment the fin ina horizontal plane and introduce a steam conduit pipe between upper andlower fin segments. Steam passed through this conduit pipe greatlyenhances a tall fins melting capability.

When the tank car gets to its destination, steam is introduced throughthe pipes 46 and 55 and courses up through the conduit sections 44 and50, then into the internal conduits 64 and 65 and also into thelowermost half oval conduits30a and 30b. The steam then courses'throughthese conduits toward the heads 12 of the tank and the headers 35, whereit then passes upwardly and divides itself, supplying steam to all theremaining conduits 30, the three upper conduits 30a and 30b, and conduit30c. Steam, and condensate as it forms, flows through respectiveconduits towards the opposite end of the tank, down through the headers35 and back towards the center of the tank through the lowermost halfoval conduits 30a and 30b to the conduit sections 44 and 50 and then tothe outlet pipes 47 and 56. It is interesting to note at this point thatthe external complex 22 is a split complex. The complex 22 on oppositesides of the tank 10 is actually fed with steam and drained ofcondensate through separate pipes so that a leak on one side will notincapacitate the entire complex.

The steam coursing through the external conduits 30 and headers 35immediately melts the solidified sulfur at the inner surface 26 of thetank 10, except on the heads 12, and forms a thin film of molten sulfurat this surface. At the same time, the heat transfer fin 70, beingsupplied with heat from the corresponding conduits 64 and 65 inside thetank 10, melts through the ring of solidified sulfur crust to form whatis, in fact, a split-ring. The molten core of sulfur is thus placed incommunication with the thickening film of molten surfur at the surface26 of the tank. A circulation path is established between the largeliquid core at the center of the tank and the thin liquid film againstthe tank surface 26. This dynamic circulation action promotes heattransmission by convection to the exposed solidified surfaces of thelading.

As this process continues, the thickness of the liquid film against thetank surface 26 rapidly increases. The structural strength of the splitring sulfur crust decreases until it can no longer support itself. Thesolid sulfur begins to act as a beam supported at the opposite heads 12of the tank, and a large deflection of the beam occurs at the center ofthe tank. This deflection induces additional liquid sulfur circulationfrom the bottom of the tank to the top thereof, thus speeding up themelting process. Soon the entire split ring shell or crust of sulfurdisintegrates and chunks of sulfur sink to the bottom of the tank wherethe heat source is concentrated and they are quickly melted.

Referring now to FIGURE 5, a modified form of the heating systemembodying features of the present invention is illustrated generally at120. The heating system 120 is identical to the system hereinbeforediscussed in all respects except for the additional provision of a rooffin 170 or fins (only one shown) mounted on the inner surface 26 of thetank 10.

The roof fins 170 comprise a pair of longitudinally coextensive finswelded to the inner surface 26 of the roof of the tank on its centerline CL. The fins 170 are disposed directly under the roof center lineconduits 300 so that heat from the steam in the conduits 30c dissipatesto the lading crust through the fins 170 as well as through the tankwall to its inner surface 26.

The fin or fins 170 function in a manner identical to the fins 70, ashas been pointed out. They immediately melt through the crust ofsolidified sulfur to cause another split in the crust ring. Additionalliquid circulation is effected and melting of the crust takes place atan even faster rate.

The constructions of the heating systems 20 and have now been describedin detail. Similarly, their operation and method of the invention havebeen thoroughly discussed. It should now be recognized that a partiallysolidified lading such as sulfur or the like can be melted and dispensedfaster than heretofore considered possible with heating equipment ofcomparable complexity. On the other hand, it is possible to eliminate asubstantial segment of an external heating complex, for example, andobtain comparable melting times.

It is the positioning of the conduits 30, 64 and 65, and the fins 70(and which contribute to this high rate of melting. The arrangement ofthe conduits 30a and 3012 at the bottom of the tank 10 assures rapidmelting of lading chunks which fall to the bottom. The arrangements ofthe fins 70 and 170 assure that the lading crust breaks up rapidly intochunks.

The invention has been discussed in terms of a steam heated fin or finsinternally of the tank 10. It is, however, also contemplated thatelectrically heated fins might be employed, or even some other heatingmedium. It is important only that heat be dissipated through the fins 70and 170 at a sufficient rate to melt through a lading crust quickly.

While several embodiments described herein are at present considered tobe preferred, it is understood that various modifications andimprovements may be made therein, and it is intended to cover in theappended claims all such modifications and improvements as fall withinthe true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of theUnited States is:

1. A method of rapidly melting a lading such as sulfur or the like inthe container of a tank car wherein the lading has partially solidifiedso as to define a solid outer crust with a molten inner core, comprisingthe steps of:

(a) generally applying heat around the outer surface of the container tomelt the lading within the container at the inner surface of thecontainer and foam a film of melted lading at this inner surface, an

(b) applying concentrated heat to the still solid crust, which isseparated from the inner surface of the container by the film, along alongitudinally extending line at the base of the container forsubstantially the length of the container to melt through the crust atthis line and place the inner core of molten Sulfur and outer film incommunication.

2. The method of claim 1 further characterized by and including the stepof:

(a) applying concentrated heat to the still solid crust,

which is separated from the inner surface of the container by the filmof melt, along a longitudinally extending line at the roof of thecontainer for substantially the length of the container to also melt 7through the crust and place said molten inner core in additionalcommunication with said film.

3. In a tank car including an elongated cylindrical tank, theimprovement in a heating system for rapidly melting a partiallysolidified lading such as sulfur or the like, comprising:

(a) means secured to the outer surface of said tank and adapted to carrya heating medium to apply heat generally completely around said outersurface for melting the solidified lading within the tank at the innersurface of the tank to form a film of melted lading around said innersurface,

(b) conduit means inside said tank extending longitudinally along thebase of the tank for substantially 7 the length of the tank, saidconduit means being adapted to carry a heating medium,

(c) longitudinally extending fin means on said conduit means along thebase of the tank for substantially the length of the tank and extendingradially inwardly of said tank inner surface,

(d) said fin means adapted to apply concentrated heat to the solidlading along a longitudinally extending line at the base of the tank forsubstantially the length of the tank to melt through the lading alongthis line.

4. The improvemento in heating system of claim 3 further characterizedin that:

(a) said conduit means is secured directly to the inner surface of saidtank,

(b) said fin means being mounted on said conduit means and extendingradially inwardly therefrom.

5. The improvement in heating system of claim 4 further characterized byand including:

(a) other conduit means inside said tank extending longitudinally alongthe roof of said tank for substantially the length of the tank, saidother conduit means being adapted to carry a heating medium, and

(b) -fin means on said other conduit means extending radially inwardlyof said tank inner surface.

References Cited UNITED STATES PATENTS 1,614,107 1/ 1927 Cleary.1,993,973 3/1935 McNeil. 2,624,553 1/1953 Thompson et a1. 3,143,1088/1964 Rogers.

FOREIGN PATENTS 458,785 12/ 1936 Great Britain.

CHARLES J. MYHRE, Primary Examiner

